U.S. patent application number 12/373950 was filed with the patent office on 2009-12-24 for pulverulent compounds, a process for the preparation thereof and the use thereof in lithium secondary batteries.
Invention is credited to Sven Albrecht, Stefan Malcus.
Application Number | 20090314985 12/373950 |
Document ID | / |
Family ID | 38823584 |
Filed Date | 2009-12-24 |
United States Patent
Application |
20090314985 |
Kind Code |
A1 |
Malcus; Stefan ; et
al. |
December 24, 2009 |
PULVERULENT COMPOUNDS, A PROCESS FOR THE PREPARATION THEREOF AND
THE USE THEREOF IN LITHIUM SECONDARY BATTERIES
Abstract
The present invention relates to pulverulent compounds of the
formula Li.sub.aNi.sub.bM1.sub.CM2.sub.d(0).sub.2(SO.sub.4).sub.x,
a process for preparation thereof and the use thereof as active
electrode material in.
Inventors: |
Malcus; Stefan; (Goslar,
DE) ; Albrecht; Sven; (Goslar, DE) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Family ID: |
38823584 |
Appl. No.: |
12/373950 |
Filed: |
October 11, 2007 |
PCT Filed: |
October 11, 2007 |
PCT NO: |
PCT/EP07/08848 |
371 Date: |
July 22, 2009 |
Current U.S.
Class: |
252/182.1 |
Current CPC
Class: |
H01M 4/525 20130101;
H01M 4/485 20130101; H01M 2300/004 20130101; H01M 4/1391 20130101;
H01M 2004/028 20130101; H01M 4/1397 20130101; Y02E 60/10 20130101;
H01M 10/052 20130101; H01M 2004/021 20130101; H01M 4/505 20130101;
H01M 10/0569 20130101 |
Class at
Publication: |
252/182.1 |
International
Class: |
H01M 4/52 20060101
H01M004/52 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 13, 2006 |
DE |
10 2006 049 098.3 |
Claims
1. Pulverulent compound of the formula
Li.sub.aNi.sub.bM1.sub.cM2.sub.d(O).sub.2(SO.sub.4).sub.x, in which
M1 denotes at least one element selected from the group consisting
of Fe, Co, Cr, Mg, Zn, Cu and/or mixtures thereof, M2 denotes at
least one element selected from the group consisting of Mn, Al, B,
Ca, Sr, Ba, Si and/or mixtures thereof, and
0.95.ltoreq.a.ltoreq.1.1, 03.ltoreq.b.ltoreq.0.83,
0.1.ltoreq.c.ltoreq.0.5, 0.03.ltoreq.d.ltoreq.0.5 and
0.001.ltoreq.x.ltoreq.0.03, characterized in that the secondary
particles have a compressive strength of at least 100 MPa.
2. Pulverulent compound according to claim 1, characterized in that
it has a compressive strength of at least 200 MPa.
3. Pulverulent compound according to claim 1, characterized in that
it has a compressive strength of at least 300 MPa.
4. Pulverulent compound according claim 1, characterized by a
porosity of up to 0.01 cm.sup.3/g measured according to ASTM D
4222.
5. Pulverulent compound according to claim 1, characterized by a
porosity of up to 0.008 cm.sup.3/g measured according to ASTM D
4222.
6. Pulverulent compound according to Claim 1, characterized by a
porosity of up to 0.006 cm.sup.3/g measured according to ASTM D
4222.
7. Pulverulent compound according to claim 1, characterized in that
the secondary particles have a spheroidal shape.
8. Pulverulent compound according to claim 7, characterized in that
the secondary particles thereof have a shape factor greater than
0.8.
9. Pulverulent compound according to claim 7, characterized in that
the secondary particles thereof have a shape factor greater than
0.9.
10. Pulverulent compound according to claim 1, characterized in
that the D10 value, measured according to ASTM B 822, after
compression of the material at a pressure of 200 MPa changes by not
more than 0.5 .mu.m compared with the starting material.
11. Pulverulent compound according to claim 1, characterized in
that the D90 value, measured according to ASTM B 822, after
compression of the material at a pressure of 200 MPa changes by not
more than 1 .mu.m compared with the starting material.
12. Pulverulent compound according to claim 1, characterized in
that the normalized width of the particle size distribution,
measured according to the Formula (1) D 90 - D 10 D 50 ( 1 )
##EQU00003## in which D denotes the diameter of the secondary
particles, is less than 1.4.
13. Pulverulent compound according to claim 1, characterized in
that the normalized width of the particle size distribution,
measured according to the Formula (1) D 90 - D 10 D 50 ( 1 )
##EQU00004## in which D denotes the diameter of the secondary
particles, is less than 1.2.
14. Pulverulent compound according to claim 1, characterized in
that it has a compressed density of at least 3.2 g/cm.sup.3 at a
compression pressure of 200 MPa.
15. Pulverulent compound according to claim 1, characterized in
that it has a tapped density measured according to ASTM B 527, of
at least 2.2 g/cm.sup.3.
16. Pulverulent compound according to claim 1, characterized in
that it has a tapped density measured according to ASTM B 527, of
at least 2.4 g/cm.sup.3.
17. Process for the preparation of the pulverulent compound
according to claim 1, comprising the following steps: a. provision
of a co-precipitated nickel-containing precursor having a porosity
of less than 0.05 cm.sup.3/g, measured according to ASTM D 4222, b.
mixing the precursor according to a) with a lithium-containing
component, c. calcination of the mixture with multistage heating to
temperatures of 1000.degree. C. with the use of a CO.sub.2-free
(.ltoreq.0.5 ppm of CO.sub.2), oxygen-containing carrier gas and
production of a pulverulent product, d. deagglomeration of the
powder by means of ultrasound and sieving of the deagglomerated
powder.
18. Process according to claim 17, characterized in that the
nickel-containing component is a mixed oxide, mixed hydroxide,
mixed oxyhydroxide, partially oxidized mixed hydroxide, partially
oxidized mixed hydroxy-sulphate of the metals Ni, Co, Mn, Al, Fe,
Cr, Mg, Zr, B, Zn, Cu, Ca, Sr, Ba and/or mixtures thereof.
19. Process according to claim 17, characterized in that the
lithium-containing component is lithium carbonate, lithium
hydroxide, lithium hydroxide monohydrate, lithium oxide, lithium
nitrate and/or mixtures thereof.
20. Process according to claim 17, characterized in that the
calcination of the precursor mixture is effected at a temperature
of 200-400.degree. C. for 2-10 hours in the first stage, at
500-700.degree. C. for 2-10 hours in the second stage and at
700-1000.degree. C. for 2-20 hours in the third stage.
21. Process according to claim 17, characterized in that the
calcination of the precursor mixture is effected at a temperature
of 250-350.degree. C. for 2-10 hours in the first stage, at
550-650.degree. C. for 2-10 hours in the second stage and at
725-975.degree. C. for 2-20 hours in the third stage.
22. Process according to claim 17, characterized in that the
calcination of the precursor mixture is effected at a temperature
of 250-435.degree. C. for 4-8 hours in the first stage, at
550-650.degree. C. for 4-8 hours in the second stage and at
725-975.degree. C. for 5-15 hours in the third stage.
23. Process according to claim 17, characterized in that the
carrier gas contains 20 to 100% by volume of oxygen.
24. Process according to claim 17, characterized in that the
carrier gas contains 40 to 100% by volume of oxygen.
25. Process according to claim 17, characterized in that the
reaction of the nickel-containing precursor takes place with
retention of the shape of the secondary particles and/or particle
size distribution.
26. Pulverulent compounds obtainable according to claim 17.
27. Use of the pulverulent compound according to claim 1 as
electrode material in lithium secondary batteries.
Description
[0001] The present invention relates to pulverulent compounds of
the formula
Li.sub.aNi.sub.bM1.sub.CM2.sub.d(O).sub.2(SO.sub.4).sub.x, a
process for the preparation thereof and the use thereof as active
electrode material in lithium secondary batteries.
[0002] Portable and cordless electric devices are very widely used
nowadays. Owing to the continued miniaturization of these portable
electronic devices, the demand for increasingly small and
increasingly light secondary batteries having a high energy
density, which serve as an energy source for such devices, has very
rapidly increased in recent years. Secondary batteries used are
mainly nickel metal hydride batteries as well as lithium ion
batteries. In consumer applications (e.g. mobile phone, laptop,
digital camera), virtually exclusively only lithium ion secondary
batteries occur since they have a substantially higher energy
density compared with the nickel metal hydride batteries.
[0003] This type of secondary battery is distinguished by active
materials on the cathode and anode side which can reversibly
incorporate and release lithium ions. When this battery type was
launched in the early 90s, lithium cobalt oxide LiCoO.sub.2 was
used as the electrochemically active substance for the positive
electrode. However, this LiCoO.sub.2 which currently still
dominates the market for active cathode materials in lithium ion
secondary batteries, has a disadvantage of a very high cobalt price
and greatly limited availability of cobalt. Against a background of
the greatly expanding markets for Li ion technology (i.e. power
tools, hybrid engine vehicles (HEV) as new applications), the
limited availability of cobalt gives cause for concern that
LiCoO.sub.2 alone will not be able in future to supply the market
for active cathode materials for Li ion batteries. Even at present,
more than 25% of the annual cobalt production is used in the
battery sector. Alternative cathode active materials are therefore
urgently necessary.
[0004] Inter alia, against this background, the use of LiNiO.sub.2
as active cathode material for Li ion batteries has already been
discussed for a relatively long time. Nickel is both substantially
more economical than cobalt and available in much larger amounts.
In addition, LiNiO.sub.2 has a substantially higher electrochemical
capacity than LiCoO.sub.2.
[0005] However, such an LiNiO.sub.2 has the disadvantage that, when
used in secondary batteries, it leads to insufficient thermal
stability of the battery. A significant change in the crystal
structure during the charging/discharging process furthermore means
that the long-life properties/cycle stability of the batteries with
such an active material does not meet the market requirements.
[0006] For improving the abovementioned parameters, various doping
elements for LiNi0.sub.2, such as, for example, Co, Al, Mn, Fe and
Mg, were therefore tested over the years, which led to a
significant improvement in the parameters discussed above. Example
compounds having the dopants mentioned are
LiNi.sub.0.80Co.sub.0.15Al.sub.0.05O.sub.2 and
LiNi.sub.0.33Co.sub.0.33Mn.sub.0.33O.sub.2These dopants permitted
the market launch of the nickel-containing lithium mixed metal
compounds, which are currently used in addition to the original
active material, LiCoO.sub.2.
[0007] In the case of the required, high-energy density of the
storage media (secondary batteries), a distinction may be made
between the volumetric energy density, expressed in watt
hours/litres (Wh/l), and the gravimetric energy density, expressed
in Wh/kg. The volumetric energy density of the secondary battery is
influenced, inter alia, by the electrode density (g/cm.sup.3) both
on the side of the cathode and on the side of the anode. The higher
the electrode density of the cathode or anode, the higher is the
volumetric energy density of the storage medium. The electrode
density in turn is influenced both by the production process of the
electrodes and by the active cathode material used. The higher the
density of the cathode material (for example, determined as tapped
density, compacted density or compressed density), the higher is
the resultant electrode density under otherwise constant conditions
during electrode manufacture (e.g. processes for electrode
manufacture, electrode composition). This discovery is already
reflected in some documents.
[0008] Thus, DE 19849343 A1 describes the compacted density of
lithium-containing mixed oxides of the formula LiNiCoMO.sub.2.
Here, M is at least one of the metal elements Al, Ca, Mg and/or B.
The compacted densities of these materials, the primary particles
of which have rectangular or square structure, and the secondary
particles of which are spherical, are in the range of 2.4 to 3.2
g/cm.sup.3.
[0009] In DE 19849343 A1 it is pointed out that the morphology and
particle shape of the precursor are of major importance for the
shape of the product (the LiNiCoMO.sub.2) and hence also the
compacted density thereof. Furthermore, it is stated that a higher
compacted density increases the relative packing quantity of an
active material for a positive electrode, with the result that the
capacitance of an electrochemical cell is increased. The importance
of spherical particles for achieving high compacted densities is
also mentioned.
[0010] The relationship between tapped density of the active
cathode material and electrode density and hence volumetric energy
density of the Li ion battery is described in Journal of The
Electrochemical Society, Vol. 15 (2004), 10, pages A1749-A1754.
[0011] Since a certain pressure is applied during the electrode
preparation, the tapped density or compacted density determined for
the powder need not, however, permit direct conclusions about the
electrode density when this powder is used. A compressed density of
a powder which is determined under a defined pressure represents a
variable which permits more reliable conclusions about the
electrode density with this powder. A precondition for the
abovementioned measurement of the compressed density as well as for
the electrode manufacture should be that the particles do not break
during the compression. Breaking of the particles would mean
firstly uncontrolled manufacture of the electrode and furthermore
such comminution of the particles during the electrode production
would lead to inhomogeneities. Thus, the internal fracture surfaces
of the comminuted particles would not have such good contact with
the binder and the conductive additive of the electrode as the
external surface of the particles. US 2004/023113 A1 is concerned
with the determination of the compressed density and compressive
strength of cathode powders.
[0012] Substances of the general formula
Li.sub.xM.sub.(1-y)N.sub.yO.sub.2 in which 0.2.ltoreq.x.ltoreq.1.2,
0.ltoreq.y.ltoreq.0.7, are mentioned therein. Here, M is a
transition metal and N is a transition metal differing from M, or
an alkaline earth metal. In US 2004/023113 A1, particular value is
placed on the fact that the particle size distribution must have a
defined form so that the pressure applied during the compression
during electrode manufacture can spread particularly gently over
the particle bed. In addition to the particle size distribution, it
is also mentioned that the particles of the powder should have
pores which are as small as possible and the pore volume of the
pores up to a diameter of 1 .mu.m should not exceed a value of 0.03
cm.sup.3/g (Hg porosimetry). However, no particular process
engineering measures are described for achieving said product
parameters. In the determination of the compressed density, the
powder is compressed under a pressure of 0.3 t/cm.sup.2.
[0013] In the examples, mainly lithium cobalt oxides are described.
At the abovementioned compression pressure of 0.3 t/cm.sup.3,
compressed densities in the range of 2.58-3.32 g/cm.sup.3 are
reached.
[0014] In addition to the compressed density itself, value is
furthermore placed on the fact that, after the compression of the
material, the volume fraction of the particles smaller than 1 .mu.m
is not greater than 0.1%. A significant increase in the fine
particles after the compression would indicate that particles are
destroyed during the application of pressure. Such a phenomenon
would endanger the homogeneity of the electrode.
[0015] It is however to be assumed that a pressure of 0.3
t/cm.sup.2 does not correspond to the pressures which are actually
applied during the electrode manufacture. During the electrode
manufacture, the material must be built to withstand at least a
pressure of 1 t/cm.sup.2. In JP 2001-80920 A, a pressure of 2
t/cm.sup.2 is stated in example 1 for the electrode manufacture. JP
2001-80920 A mentions the compressive strength of lithium mixed
metal oxides (LNCO), which comprise three metallic components in
addition to lithium.
[0016] The materials thus produced have a compressive strength of
0.001-0.01 N. According to this document, it is desirable for the
particles to disintegrate into their primary constituents during
the electrode manufacture, which is contrary to the argumentation
of US 2004/023113 A1. According to JP 2001-80920 A the material
which has disintegrated into smaller constituents must have a
certain flowability to enable the particles to be distributed
uniformly over the electrode.
[0017] The compressive strength of lithium mixed metal oxides is
also discussed in US 2005/0220700 Al. There, the compounds have the
formula Li.sub.pNi.sub.xCo.sub.yMn.sub.zM.sub.qO.sub.2-aF.sub.a.
Whereas US 2004/023113 A1 only states the value 0.3 t/cm.sup.2 for
the compressive strength, compressive strengths of at least 50 MPa
are stated in US 2005/0220700 A1 for the lithium mixed metal
compounds, which corresponds to 0.5 t/cm.sup.2. However, the
formula for the relevant compounds in US 2005/0220700 A1 is defined
substantially more narrowly than that in US 2004/023113 A1. Thus,
manganese is a fixed constituent of all compounds in US
2005/0220700 A1. US 2005/0220700 A1 does not consider why the
compounds mentioned have a particular compressive strength. Only a
defined particle size range and a defined range for the specific
surface area of the materials are mentioned. Particular process
engineering peculiarities which make the material particularly
pressure-resistant are not mentioned.
[0018] US 2005/0220700 A1 discloses compounds which contain
fluoride as a further anionic component in addition to the anionic
oxygen. EP 1450423 A1 claims an active material for positive
electrodes of a nonaqueous secondary battery, which material can be
expressed substantially by a lithium mixed metal oxide compound,
that has sulphate anions in the range from 0.4% by weight to 2.5%
by weight. The high proportion of sulphate anion is intended to
ensure that the carbon content in the end product (substantially as
alloy to Li.sub.2CO.sub.3) is kept low.
[0019] It is an object of the present invention to provide a
lithium mixed metal oxide in which the secondary particles are not
broken or not comminuted during the electrode manufacture
(cathode).
[0020] The preservation of the secondary particle during electrode
manufacture is of major importance for the homogeneity of the
electrode. At the same time, it should be possible to achieve a
high electrode density and good electrochemical properties with
such a lithium mixed metal oxide. The object of the present
invention is furthermore to provide a process for the preparation
of the lithium mixed metal oxide.
[0021] The object is achieved by a pulverulent compound of the
formula Li.sub.aNi.sub.bM1.sub.cM2.sub.d(O).sub.2(SO.sub.4).sub.x
(subsequently also referred to as LNMOS or lithium mixed metal
oxides), in which M1 denotes at least one element selected from the
group consisting of Fe, Co, Cr, Mg, Zn, Cu and/or mixtures thereof,
M2 denotes at least one element selected from the group consisting
of Mn, Al, B, Ca, Sr, Ba, Si and/or mixtures thereof, and
0.95.ltoreq.a.ltoreq.1.1, 0.3.ltoreq.b.ltoreq.0.83,
0.1.ltoreq.c.ltoreq.0.5, 0.03.ltoreq.d.ltoreq.0.5 and
0.001.ltoreq.x.ltoreq.0.03, the secondary particles of which have a
compressive strength of at least 100 MPa.
[0022] Compounds which are part of the invention are shown in the
table below.
TABLE-US-00001 Compound No. a b M1 c M2 d x 001 1.09 0.333 Co 0.333
Mn 0.333 0.015 002 1.05 0.50 Co 0.20 Mn 0.30 0.015 003 1.03 0.77 Co
0.13 Mn 0.10 0.009 004 1.03 0.80 Co + Mg 0.10 Mn 0.10 0.007 005
1.03 0.70 Co 0.10 Mn + Al 0.20 0.006 006 1.05 0.30 Co 0.30 Mn + Al
0.40 0.015 007 1.03 0.80 Co 0.17 Al 0.03 0.005 008 1.04 0.75 Co +
Fe 0.20 Al 0.05 0.006 009 1.02 0.80 Co 0.16 Al + B 0.04 0.003 010
1.03 0.80 Co 0.17 Sr 0.03 0.002 011 1.03 0.60 Mg 0.10 Mn 0.30 0.004
012 1.04 0.45 Mg 0.10 Mn 0.45 0.009 013 1.02 0.333 Co 0.333 Mn
0.333 0.015 014 1.04 0.45 Co 0.10 Mn 0.45 0.009 015 1.04 0.40 Co +
Mg 0.20 Mn 0.40 0.007 016 1.02 0.77 Co 0.20 B 0.03 0.003 017 1.03
0.60 Co 0.20 Mn 0.20 0.005 018 1.03 0.80 Fe 0.10 Mn 0.10 0.004 019
1.02 0.70 Co 0.25 Al + Ca 0.05 0.002 020 1.01 0.80 Co 0.16 Al 0.04
0.001
[0023] The secondary particles of the pulverulent LNMOS compound
according to the invention preferably have a compressive strength
of at least 200 MPa, particularly preferably of at least 300 MPa.
Secondary particles are understood as meaning compact particles
composed of a multiplicity of primary particles. Primary particles
are particles which form from nuclei, for example during a
crystallization process.
[0024] The compressive strength of the secondary particles
according to the invention can be determined by the method
mentioned in US 2004/0023113 A1, page 6, Example 1.
[0025] The pulverulent lithium mixed metal oxides according to the
invention are distinguished by their very low porosity. According
to the invention, the pulverulent lithium mixed metal oxides have a
porosity, measured according to ASTM D 4222, of up to 0.01
cm.sup.3/g, preferably up to 0.008 cm.sup.3/g, with particular
preference up to 0.006 cm.sup.3/g.
[0026] The pulverulent lithium mixed metal oxide according to the
invention can be prepared both in spheroidal and in regular
(non-spheroidal) particle shapes.
[0027] Preferred pulverulent lithium mixed metal oxides according
to the invention are distinguished in particular by the spheroidal
particle shape of the secondary particles, the shape factor of
which has a value greater than 0.8, with particular preference
greater than 0.9.
[0028] The shape factor of the secondary particles can be
determined by the method mentioned in U.S. Pat. No. 5,476,530,
columns 7 and 8 and FIG. 5. This method determines the shape factor
of the particles, which is a measure of the sphericity of the
particles. The shape factor of the secondary particle can also be
determined from the scanning electron micrographs of the
materials.
[0029] The shape factor is determined by evaluating the particle
circumference and the particle area and determining the diameter
derived from the respective variables. Said diameters are obtained
from
d.sub.U=U/.pi. d.sub.A=(4A/.pi.).sup.1/2.
[0030] The shape factor of the particles f is derived from the
particle circumference U and the particle area A according to:
f = ( d A d U ) 2 = ( 4 .pi. A U 2 ) ##EQU00001##
[0031] In the case of an ideal spherical particle, d.sub.A and
d.sub.U are of equal magnitude, and a shape factor of exactly one
would result.
[0032] FIG. 1 shows, by way of example, an image, recorded using a
scanning electron microscope (SEM), of the pulverulent lithium
mixed metal oxide according to the invention, which was prepared
according to Example 1.
[0033] Preferably, the pulverulent lithium mixed metal oxides
according to the invention have a D10 value, measured according to
ASTM B 822, which changes by not more than 1 .mu.M, preferably by
not more than 0.5 .mu.M, after compression of the powder at a
pressure of 200 MPa compared with the starting powder.
[0034] A decrease in the D10 value after the compression means that
a fraction of the particles has been broken into smaller particles.
Thus, the change in the D10 value is a quantitative measure for
determining the compressive strength of the powders according to
the invention.
[0035] Preferably, the pulverulent lithium mixed metal oxides
according to the invention have a D90 value, measured according to
ASTM B 822, which changes by not more than 1 .mu.m after
compression of the powder at a pressure of 200 MPa compared with
the starting material.
[0036] FIG. 2 shows, by way of example, a scanning electron
micrograph of the pulverulent lithium mixed metal oxide according
to the invention after compression at 200 MPa, which lithium mixed
metal oxide was prepared according to Example 1.
[0037] FIG. 2 shows that the spheroidal secondary particles have
retained their shape even after compression and have not broken
into fragments of a spheroidal particle. It is clear from this that
the material bed of the compound prepared according to Example 1
withstands a pressure of 200 MPa without the particles
breaking.
[0038] The pulverulent lithium mixed metal oxides according to the
invention preferably have a normalized width of the particle size
distribution, measured according to the Formula (1)
D 90 - D 10 D 50 ( 1 ) ##EQU00002##
in which D denotes the diameter of the secondary particles, of less
than 1.4, particularly preferably less than 1.2.
[0039] Preferably, the pulverulent lithium mixed metal oxides
according to the invention have a compressed density of at least
3.2 g/cm.sup.3, preferably of at least 3.5 g/cm.sup.3, measured at
a compression pressure of 200 MPa.
[0040] The pulverulent lithium mixed metal oxides according to the
invention are also distinguished in that they have a tapped density
of at least 2.2 g/cm.sup.3, preferably of at least 2.4 g/cm.sup.3,
measured according to ASTM B527.
[0041] The invention furthermore relates to a novel process for the
preparation of pulverulent lithium mixed metal oxides according to
the invention.
[0042] The invention therefore relates to a process for the
preparation of the pulverulent lithium mixed metal oxides,
comprising the following steps: [0043] a. provision of a
co-precipitated nickel-containing precursor having a porosity of
less than 0.05 cm.sup.3/g, measured according to ASTM D 4222,
[0044] b. mixing the precursor according to a) with a
lithium-containing component and production of a precursor mixture,
[0045] c. calcination of the precursor mixture with multistage
heating to temperatures of 1000.degree. C. with the use of a
CO.sub.2-free (.ltoreq.0.5 ppm of CO.sub.2), oxygen-containing
carrier gas and production of a pulverulent product, [0046] d.
deagglomeration of the powder by means of ultrasound and sieving of
the deagglomerated powder.
[0047] For the preparation of lithium mixed metal oxides according
to the invention, nickel-containing precursors which have a low
porosity of less than 0.05 cm.sup.3/g, preferably of less than 0.04
cm.sup.3/g, particularly preferably of less than 0.03 cm.sup.3/g,
are required. Suitable nickel-containing precursors are in
particular mixed oxides, mixed hydroxides, mixed oxyhydroxides,
partially oxidized mixed hydroxides, partially oxidized mixed
hydroxysulphates of the metals Ni, Co, Mn, Al, Fe, Cr, Mg, Zr, B,
Zn, Cu, Ca, Sr, Ba and/or mixtures thereof.
[0048] The preparation of the co-precipitated nickel-containing
precursor is carried out by precipitation from aqueous metal salt
solutions at a PH of 8-14, preferably of 9-13, by feeding alkali
metal hydroxide solutions and optionally ammonia, in gaseous form
or as an aqueous solution. Although the reaction to give the
nickel-containing precursor can be effected batchwise or
semicontinuously, this precipitation reaction is preferably carried
out continuously. In the continuous process, metal salt solution
and the alkali metal hydroxide solution are fed simultaneously to a
precipitation reactor with continuous removal of the product
suspension. Suitable metal salts are water-soluble metal salts,
e.g. nitrates, sulphates, halides, such as for example, chlorides
or fluorides. When carrying out the precipitation, hydroxides of
the alkali metals, preferably sodium hydroxide or potassium
hydroxide, are used as alkali metal salt solutions.
[0049] The nickel-containing precursors can be prepared both in
spheroidal and in nonspheroidal particle shape, the preparation of
the first-mentioned being carried out in the presence of ammonia or
ammonium salts.
[0050] For the preparation of the lithium mixed metal oxides, the
co-precipitated nickel-containing precursors are thoroughly mixed
with a lithium-containing component so that a homogeneous mixture
of the components is produced. Lithium carbonate, lithium
hydroxide, lithium oxide, lithium nitrate, lithium hydroxide
monohydrate and/or mixtures thereof are preferably used as the
lithium-containing components. For the reaction of the precursor
mixture to give the lithium mixed metal oxides according to the
invention it is important for the thermal treatment (calcination)
to be effected over a plurality of temperature stages. Preferably,
the calcination is carried out in three stages, the precursor
mixture being heated at a temperature of 200-400.degree. C. for
2-10 hours in the first stage, at 500-700.degree. C. for 2-10 hours
in the second stage and at 700-1000.degree. C. for 2-20 hours in
the third stage. Preferably, the precursor mixture is calcined at a
temperature of 250-350.degree. C. for 2-10 hours in the first
stage, at 550-650.degree. C. for 2-10 hours in the second stage,
and at 725-975.degree. C. for 2-20 hours in the third stage,
particularly preferably at a temperature of 250-350.degree. C. for
4-8 hours in the first stage, at 550-650.degree. C. for 4-8 hours
in the second stage and at 725-975.degree. C. for 5-15 hours in the
third stage.
[0051] As a result of the temperature hold stages and associated
controlled reaction a material is obtained which has no secondary
particle agglomerates that are strongly sintered together.
Agglomerates that are strongly sintered together are understood as
meaning agglomerates which do not disintegrate into the individual
secondary particles in the case of ultrasound sieving. Such a
material without agglomerates which are strongly sintered together
has the advantage that milling, as is usually required after
calcination, can be dispensed with. Milling has the disadvantage
that destruction of individual spheroidal secondary particles leads
to the formation of angular and square-edged particles. It is in
particular these particles which, during electrode manufacture,
owing to their shape, result in further particles being destroyed
within the material bed under high pressure.
[0052] The lithium mixed metal oxide which is obtainable after the
calcination according to the invention and may be present in
slightly agglomerated form is subjected to gentle deagglomeration
by means of ultrasound and subsequent sieving. The ultrasound
causes the isolated, loose agglomerates which are optionally formed
during the calcination, to disintegrate in a gentle manner into
their constituents (secondary particles), but without the secondary
particles themselves being destroyed.
[0053] Furthermore, it is important that the reaction to give the
LNMOS takes place in an oxygen-containing carrier gas atmosphere
which is free of CO.sub.2. A CO.sub.2-free carrier gas atmosphere
is understood as meaning a carrier gas which contains .ltoreq.0.5
ppm (part per million) of CO.sub.2. The absence of CO.sub.2 in the
carrier gas prevents incorporation of the CO.sub.2 into the end
product, with the result that formation of crystal lattice defects
is reduced.
[0054] Preferably, the carrier gas contains 20 to 100% by volume,
particularly preferably 40 to 100% by volume, of oxygen. The
process according to the invention is distinguished by the fact
that the reaction of the nickel-containing precursor takes place
with retention of the shape of the secondary particles and/or
particle size distribution.
[0055] The process according to the invention makes it possible,
for example, to convert the spherical nickel-containing precursors
having a very narrow particle size distribution into the lithium
mixed metal oxide with retention of the shape of the secondary
particles.
[0056] The pulverulent lithium mixed metal oxides according to the
invention are suitable in particular for the production of
secondary lithium batteries. Preferably, they are used as electrode
material (anode, cathode) for lithium secondary batteries together
with the material known to the person skilled in the art.
[0057] The invention is explained in more detail below with
reference to the following example.
EXAMPLE 1
[0058] A spheroidal
Ni.sub.0.33CO.sub.0.33Mn.sub.0.33(O).sub.0.2(OH).sub.1.8(SO.sub.4).sub.0.-
01 was used as co-precipitate Ni precursor. This material had a
porosity of 0.0372 cm.sup.3/g. An Li.sub.2CO.sub.3 of <40 .mu.m
(Chemetall) was dry-blended with the Ni precursor in the molar
Li/(Ni+Co+Mn) ratio of 1.05:1.00. The dry blend thus formed (also
referred to as premix) was then placed in an oven at room
temperature and first heated to 300.degree. C. and kept at this
temperature for 6 hours. The heating of the material and the entire
oven process were effected with the use of oxygen as a carrier gas
stream which is substantially free of CO.sub.2 (.ltoreq.0.5 ppm).
At said 300.degree. C., controlled release of water from the
nickel-containing precursor took place.
[0059] After this temperature hold stage, the material was heated
further to 600.degree. C. and kept at this temperature for 6 hours.
At this oven temperature a very controlled reaction of the two
starting components to give
Li.sub.1.04Ni.sub.0.33Co.sub.0.33Mn.sub.0.33O.sub.2(SO.sub.4).sub.0.-
01 took place. The reaction temperature was deliberately kept low
in order to be able to achieve a slow and hence controlled reaction
of the two components to give the end product. By means of this
controlled reaction, the formation of crystal lattice defects and
the significant inclusion of pores in the particle structure were
avoided. A "breathing"/gas expulsion from the material during the
reaction is permitted. Finally, the material is heated to
860.degree. C. and then kept at this temperature for 10 hours in
order to carry out ripening of the crystals and to produce high
crystallinity.
[0060] Thereafter the material is brought to room temperature and
then poured directly on to a sieve having a mesh size of 50 .mu.m.
The sieve was additionally equipped with an ultrasound generator
having an ultrasound power of 200 W. The deagglomerated and sieved
material thus obtained has a tapped density of 2.2 g/cm.sup.3. The
porosity of the material was 0.0029 cm.sup.3/g. The D10, D50 and
D90 values were 5.67 .mu.m, 8.96 .mu.m and 13.62 .mu.m. For the
normalized particle size width, the value of (13.62 .mu.m-5.67
.mu.m)/8.96 .mu.m=0.89 was obtained therefrom.
[0061] The material had a density of 3.0 g/cm.sup.3 after the
determination of the compressed density at 100 MPa, and a density
of 3.3 g/cm.sup.3 after the determination at 200 MPa.
[0062] The D10 value had decreased by 0.2 .mu.m compared with the
original material after determination of the compressed density at
a pressure of 100 MPa, and the D10 value had decreased by 0.4 .mu.m
compared with the original material at a pressure of 200 MPa. The
particle size distributions of the material before the compression
and after the compression at a pressure of 200 MPa are shown in
FIG. 3.
[0063] The LNMOS prepared in the example was measured as positive
active material in an electrochemical half-cell with lithium metal
as the negative electrode (anode). The electrolyte used was a 1:1:1
mixture of ethylene carbonate, dimethyl carbonate and diethyl
carbonate, which contained LiPF.sub.6 in a concentration of 1
mol/l. The positive electrode consists of 83% by weight of active
material, 10% by weight of carbon black super P and 7% by weight of
polytetrafluoroethylene (PTFE) as binder. The initial
electrochemical capacity was determined in a voltage range of 2.75
to 4.3 V at a constant current rate of 0.1 C (10 hours per complete
charging or discharging). Under said measuring conditions an
initial discharge capacity of 160 mAh/g was achieved.
[0064] The electrochemical cyclic behaviour was determined in a
voltage range of 2.75 to 4.3 V at a constant current rate of 1 C (1
hour per complete charging or discharging). After 40
electrochemical charging and discharging cycles, the cell still
exhibited 98.5% of the initial discharge capacity at a constant
current rate of 1 C.
* * * * *